Already put new spark plugs and wires and a brand new ignition coil....what else could it be? I know it's about to get pretty expensive

 

There may be a hundred reasons for a blinking check engine light. There's no point in guessing. Get a code reader attached and find out. Many auto parts stores like PepBoys ot AutoZone will do it for free.
The longer you put it off the more expensive it will be.

 

I did get a code reader attached at Auto Zone and it said spark plugs and wires. I changed the spark plugs and wires and the Ignition coil and the check engine light is still blinking

 

Code readers don't say "spark plugs and wires" They say something like Pxxxx where the x's are numbers. Then you look up the number to see what the error code refers to. Not all code readers can get all error codes. You might have to go somewhere else where they have a better code reader. Sounds like the "code reader" at the store you went to said "we need to sell some spark plugs and wires today". Get the actual numbers and write them down. Then google them. There are many sites on the internet that will decode OBD II (on-board diagnostic) codes and point you in the right direction for servicing. A blinking light needs immediate attention.

 

Before doing any manitenance the code reader showed an error code of P0303

After changing spark plugs, wires and ignition coil the code still reads P0303 which is a cylinder #3 misfire

My mechanic is clueless to what else it could be, as am I

 

If it's misfiring on a particular cylinder and you're sure it's not a spark misfire, then the next logical thing would be to see if it's misfiring because of a fuel problem. Perhaps the fuel injector for that cylinder is clogged. Before pulling things apart, try something cheap like a can of fuel injector cleaner. Might work, can't hurt.
Make sure the fuel injector is getting a signal and that there's a proper ground. After that, you might need to pull out the fuel injector and either clean (un-clog) it, or replace it.